November 14, 2016

This small chapter is included in this blog to acquaint the readers with nomenclature of perforator based flaps. To that end the compiler of this blog wrote to Sameer Kumta and Leena Jain two leading microvascular surgeons in private practice in Mumbai India and the following communication was sent to them.

The human circulatory system being centrifugal and because the integument is the body’s outermost layer the vessels that supply it need perforce to pierce fascial envelopes to supply and drain it. The word perforator was majorly used by Ian Taylor the well known plastic surgeon from Australia whose voluminous work was published in the late eighties and nineties, mainly in the British Journal of Plastic Surgery and involved a very large number of cadaveric dissections. These dissections involved the vascular network surrounding the neural network and it was he who conceptualised the idea of an angiosome to define territories of vascular supply based on independent perforator vessels.

The word ‘envelopes’ at the beginning of the preceding paragraph is used in the plural because fascia is present in multiple planes in the body. For example, it envelopes the arteries themselves and is also present as an inter-muscular septum as well as an independent entity which encases the muscle (perimyceum). The fascia is also present in the subcutaneous plane through which the vessels pass to ultimately supply the skin. The question that needs to be clarified is at what level does a vessel come to be called as a perforator. For example the historic Sushruta flap or the forehead flap is now known to be supplied by the supra-trochlear vessel which penetrates the local deep fascia after traversing a bony gutter in the orbit to supply the skin over a large area of the forehead. Could this flap then be called a perforator flap because the concerned vessel pierces the local deep fascia? A similar question can be posed about the well-known ‘groin’ flap based on the superficial external iliac artery. This vessel is a branch of the femoral artery and is termed as a direct cutaneous artery in the existing classification though it has pierced the femoral sheath which in fact is a condensed form of the regional deep fascia and what is more a flap is now based on one of its very tiny branches which passes through the subcutaneous tissue to supply a sizable area of skin and can be transferred by way of a micro-vascular transfer. Is this flap a perforator flap? The reply of doctors Kumta and Jain to this communication by the compiler of these short notes is reproduced below. The relevant diagrams were drawn jointly by the compiler and the two expert contributors.

Introduction

Koshima and Soeda in 1989 first described perforator flaps to differentiate an adipocutaneous flap from the conventional fasciocutaneous flaps to highlight the fact that the supra and subfascial plexus were not essential for a flap’s survival. With over 400 perforators more than 0.5 mm in diameter being available across the body, any part of the body can be thus considered as a potential perforator flap donor site, in line with the principle of a free-style perforator flap. This march from conventional flaps to ‘free style’ flap has been revolutionary due to the multiplicity of donor sites that can be harvested in various parts of the body.

To begin with the definition; a perforator flap is one that receives its blood supply from a fascia-perforating vessel whether directly perforating or indirectly perforating it after traversing the muscle or the intermuscular septum. To understand the basic course of a perforator, Werner Spalteholz (1893) has classified them into a direct or a pure artery that directly enters the skin (direct cutaneous perforator – DCp) and an indirect or impure artery that penetrates the muscle / septum and then supplies the skin (musculocutaneous perforator – MCp and septocutaneous perforator – SCp). This course in practical terms determines whether or not intramuscular dissection would be required while harvesting a particular perforator flap.

Nomenclature

Newer perforator flaps continue to be described; however there is no uniform anatomical nomenclature of perforator flaps. The basic requirements to standardise a nomenclature are:

Should be simple to understand and reproducible by any micro-surgeon

Should be anatomically sound

define the source vessel (vascular anatomy)

define the anatomic muscle dissected if any (surgical anatomy)

define the type of perforator (perforator anatomy)

Should be clinically significant in stating whether superfine micro-vascular anastomosis is required or not.

According to the Gent consensus, a perforator flap should be named after the nutrient artery or vessels and not after the underlying muscle. If there is a potential to harvest multiple perforator flaps from one vessel, the name of each flap should be based on its anatomical region or muscle. For example, the nutrient vessel [lateral circumflex femoral artery (LCFA)] plus the muscle name (vastus – lateralis) yields the flap name, LCFAP-vl. This classification does not however, define the type of perforator that has been dissected- septocutaneous / musculocutaneous and does not mention the level of dissection – perforator level/ source vessel level.

Sinna et al, proposed the following modifications to the above nomenclature:

At least three elements must be accurately described.

The first term specifies the name of the proximal vessel, as suggested by Hallock.

The second term defines the extent of vascular dissection, as suggested by Kim.

The third term identifies the muscle in addition to the type of perforator (a musculocutaneous, septocutaneous, or direct cutaneous perforator), characterized in the Gent consensus.

J T Kim, provides an anatomical classification system which signifies the course of perforator, its source vessel and the muscle being traversed if any.

A: DIVISIONS OF NOMENCLATURE

Perforator flaps can be categorized into :

When based on DCp/ SCp, it is named according to the proximal vessel name.

When based on MCp, it is named according to the muscle it perforates.

Whether the proximal source vessel is harvested or dissection is stopped at perforator level itself would indicate the level of anastomosis that is at ‘perforator level’ or ‘source vessel’ level; the former is technically superior as it needs super microsurgical anastomosis. This forms the basis of nomenclature of the flap whether it is a perforator based flap (anastomosis at perforator level) or a perforator flap (anastomosis at source vessel level).

B: BASIS OF NOMENCLATURE

DCp is the perforator sprouting from the proximal vessel to dermis without traversing the muscle or deep fascia, and mostly found in face, perineum and so on.

SCp is the one piercing the intermuscular septum

MCp, is one piercing the muscle and requires intramuscular dissection of the perforator.

C: APPLICATION OF NOMENCLATURE

LATERAL THORACIC REGION

In accordance with Kim’s classification, flaps from the lateral thoracic region could thus be described and comprehended in the following manner:

“Latissimus dorsi perforator-based flap”: based on a musculocutaneous perforator and dissection stopped at the level of perforator itself.

“Latissimus dorsi perforator flap”: based on a musculocutaneous perforator and dissection done till the source vessel.

“Thoracodorsal perforator based flap”: based on a septocutaneous perforator and dissection stopped at the level of perforator itself, no dissection of the main proximal vessel.

“Lateral thoracic perforator flap”: based on a direct cutaneous perforator from the lateral thoracic artery, dissection is done till the proximal artery.

Figures below first show the basic design of the branches that ensue from the femoral artery. The wonder that is natural symmetry, means that the same figure can be used to describe the arteries around the shoulder or around the lateral thoracic region by changing the names of the vessels. Nomenclature of perforator flaps harvested from the lateral thoracic region; as well as flaps based on the femoral system are also included in the figures.

LOWER LIMB

In the thigh, the anterolateral thigh flap can be elevated based on SCp or MCp:

Perforator based flap: no sacrifice of source artery, suffix of anatomic direction or area

MCp: name of muscle + perforator based flap

SCp / DCp: name of source artery + perforator based flap

The above nomenclature proposed by Kim is easy to follow and can be comprehended by surgeons across the globe. Uniformity in nomenclature of perforator flaps cannot be over- emphasized as perforator flaps are the order of the day in reconstructive surgery.